Plastic Lenses

Plastic lenses are not only lighter in weight, they are especially adaptable
to tints. These lenses are normally dipped into a heated dye and the tint
is slowly absorbed into the plastic. To make a darker tint, the lenses are simply left in the liquid longer. To make a "gradient" tint in which the top of the lens is darker than the bottom, the lens is slowly lowered (upside-down) into the dye. Since the top of the lens enters the die first and is withdrawn last, it spends more time in the dye and becomes darker than the lens bottom.

Tint Darkness

In addition to color, the intensity or "darkness" of a tint must be specified. Tint intensity is expressed as a percentage of the light it blocks. "Fashion" tints are usually in the
10-20% range. Sunglass tints should be at least 60% intensity to provide adequate protection. For most outdoor activities and daytime driving a 70-80% intensity works well. For sports like mountain climbing or snow skiing, 90% tints and above are recommended.

Tints are also described using a "1 to 4" numbering system instead of percentages for darkness ratings. Number one is almost clear...number four is darkest. Sunglasses are usually produced in darkness number three. Darkness number four is too dark for most wearers, but can be an ideal choice for high-glare environments like mountain climbing.

Choosing Tint Color

Because white light is made up of many colors, picking tints carefully can improve the performance of your eyewear in specific environments and activities.

A rose tint is cosmetically appealing, soothing to the eyes, and seems to provide a degree of relief when the wearer is working in brightly lit offices. A rose tint is often recommended for computer users to help reduce eyestrain and glare.

A yellow tint makes objects appear sharper against a blue or green background. Blue light bounces or scatters the most and can create a kind of glare known as "blue haze". Yellow tints are sometimes marketed as "blue blockers" because they are fairly opaque to blue light. Yellow tints are good for overcast, hazy or foggy conditions and are a favorite of shooters, skiers and pilots. Yellow is generally NOT a good choice for any activity that depends on accurate color perception.

Brown and amber tints work well in variable light conditions and provide good contrast because they filter some blue light, although not as strongly as a yellow tint. Brown lenses are good general purpose lenses and work especially well for sports where judging distance is important like tennis and golf.

Green tints filter some blue light and enhance contrast in low-light conditions. The human eye is most sensitive to green wavelengths of light so green tints offer the highest contrast and greatest visual acuity of any tint.

Grey - A grey tint provides good protection from glare and keeps distortion of colors to a minimum. Grey is sometimes referred to as a "tru-color" tint. Grey is available in a wide range of densities and is an excellent choice for general use and driving. Grey is the most popular sunglass tint.

G-15 - This sunglass tint is sometimes called the "Ray-Ban" tint. It is essentially a combination of a grey and green tint that transmits 15% (blocks 85%) of the light.

Purple is balanced color which provides natural color perception while shading the eye. Purple lenses can be a good choice for hunters.
 

Blue can be a good choice for fashion tints in lighter shades. If the lenses are intended for outdoor use, remember that blue tints can increase glare. In this case, consider using a brown or grey lens combined with a blue mirror coating.

A “gradient tint” describes a lens with a darker tint at the top, fading gradually to little or no tint at the bottom of the lens. This provides additional protection from light coming from above, without blocking too much light from straight ahead or below. Gradient sunglasses work particularly well for driving; glare coming through the windshield is blocked but the speedometer and other instruments are easy to see through the lighter bottom portion of the lens.

Double gradient tint - A “double gradient tint” describes a lens with a darker tint at the top and bottom of the lens, and a medium tint in the center of the lens. Double gradient tints are good for skiers, because glare coming from above (sun) and below (snow) is heavily blocked but a clearer viewing area is present in the middle of the lens.

Mirror Lenses - A mirror coating applied to the outside of a lens helps deflect reflected light. The outside of the lens looks just like a mirror but the wearer sees only the tint.

"Fun" Photochromics - Some plastic photochromic lenses are available in unusual colors. These lenses are one color when UV light is not present but change to a totally different color when activated by UV. There are teal-blue lenses that change to green, yellow lenses that change to orange, and red lenses that change to purple.

Ultraviolet (UV) Protection - Lenses with ultraviolet (UV) protection prevent potentially harmful radiation from reaching your eyes. According to United States Federal law, all sunglasses sold in the United States must have UV protection. However, many low-priced sunglasses for sale through street vendors do not comply with this rule. Using tinted sunglass lenses without UV protection is extremely damaging to your eyes, because the dark tint causes your pupils to dilate and increases the surface area of your retina that can be damaged by the ultraviolet radiation.